Simultaneous Introgression and Mapping of Hessian Fly Resistance from Aegilops tauschii in Wheat

Hessian fly (HF; Mayetiola destructor), a member of the gall midge family of plant-parasitic insects, is a serious insect pest of wheat (Triticum aestivum) that results in 5-10% annual yield loss in the United States alone. Thirteen biotypes of HF, designated as A-L and GP, have been reported based on their infestation of known sources of resistance. GP is most prevalent in the Great Plains and is one of the most virulent biotypes. Seven of the 35 resistance genes documented to date provide resistance to the GP biotype, and all GP-effective resistance genes are mapped on short arm of chromosome 1A. HF resistance genes and avirulence effectors in the fly fit the gene-for-gene model. Thus, deployment of a single resistance gene produces a strong selection pressure on the insect populations and resistance is often rapidly defeated. It is imperative to continue with the discovery of new genes that can be deployed in wheat breeding. A new HF resistance gene was identified from the diploid D-genome relative, Aegilops tauschii, by mapping in a direct introgression backcross population with hard red winter wheat cultivar ‘Overley’ . Phenotypic screening of BC₃F_2:3 lines indicated that resistance is conferred by a single dominant gene. Genotyping-by-sequencing (GBS) and bulked-segregant RNAseq and RenSeq were used to genotype the population and map the HF resistance. Genotypic analysis has shown that the gene is present on the distal end of the long arm of chromosome 3D, and positioned around 573Mb with an introgression size of ~7.5Mb. Developing wheat varieties with host resistance, particularly with well-characterized genes pyramided by marker assisted selection, is an effective and sustainable way to control HF and other insects. This germplasm will be available for the plant breeding community through the K-State Wheat Genetics Resource Center.